1. Field of the Invention
The present invention relates to a vise, which is mounted on the bed of a milling or grinding machine thereby to fix a work in position.
2. Description of the Prior Art
A usual vise is made to have its one clamping jaw fixed to the base thereof and its other clamping jaw made movable toward and away from the stationary clamping jaw by means of a threaded spindle. Especially in high-pressure vises the stationary clamping jaw tends to become yielded because the base of the vise is bent upwards. In order to avoid such bending of the vise base, which apparently will prevent accurate 90.degree.-surfaces of the work piece a separate U-shaped tie element has been proposed in U.S. Pat. No. 2,882,656. The front leg portion of the tie element is pivotably mounted at the stationary clamping jaw by means of laterally projecting pins which are supported in arcuate recesses of the stationary clamping jaw. The rear leg portion of the tie element has a thread hole for engagement with the threaded spindle. When a work piece is clamped between the jaws the tie element is deformed however, the base is relieved from reaction forces and the stationary clamping jaw remains in its vertical position.
In the known vise the lateral pins indeed provide for a swivelling mounting of the tie element however, the whole reaction forces of the clamping forces are transmitted to the pins which in case of high-pressure vises would become distorted. Furthermore, it is necessary to have both pins precisely aligned in order to prevent that the pins are non-uniformly loaded. In practice this would result in high production costs. Last but not least the pivot axis of the tie element should have a maximum distance from the base in order to prevent that the stationary clamping jaw becomes yielded. If large dimensioned pins are used which are required with high-pressure vises the pivot axis necessarily comes nearer to the base and in fact would lie on a level within the lower half of the clamping jaw.
From German Patent No. 30 00 162 a similar vise is known which however has the disadvantage that the front leg portion of the U-shaped tie rod has a planar upper end face which contacts a complementary inner face of the stationary clamping jaw and is fastened thereto by a pair of screw bolts. Because of the rigid connection between the tie element and the stationary clamping jaw the latter becomes tilted by distorsion of the tie element when high clamping forces are applied. Therefore, a precise squaring of a work piece is not possible.